It is 25 years since the world's worst industrial disaster - India's Bhopal tragedy. Survivors and local residents held a candle-lit vigil to remember the victims of a lethal gas leak from a Union Carbide pesticide plant.

According to government figures, the toxic fumes killed about 15,000 people - though some activists put the long-term toll at twice that. Thousands of people still suffer chronic illnesses related to the leak.

As yet, no one has been brought to account for the disaster, with court cases still pending.

Al Jazeera's Nilanjan Chowdhury reports from Bhopal on the continued suffering of the city's residents.